Model railway train systems are typically powered by current supplied through the tracks. A transformer electrically connected to a conventional home wall outlet converts household alternating current into current suitable for powering the train. The HO standard model railway system uses direct current, while three-rail model railway systems such as Lionel use alternating current. The transformer is connected to the railway track to provide a potential difference between the rails. Typically, the potential difference is supplied to the wheels on the locomotive or other rail car of the model railway system via the rails to an electric motor on the locomotive or lights on a car. Alternatively, a third rail can be used to supply power via a pickup roller to the electric motor or lights.
The speed of travel of the model train on the track is generally controlled by the amplitude of the voltage applied to the rails. However, when a remote-control system is used, such as the Lionel TMCC (TrainMaster Command Control) for three-rail 0-gauge or the DCC (Digital Command Control) for HO, the voltage remains constant on the track, while an internal circuit in the engine receives digital commands through the track or by radio and controls the amount of track voltage reaching the motors. The method of reversing the direction of travel of the train varies from control system to control system.
It is known in the art to control certain aspects of the operation of a model railway train system by superimposing a DC control signal on the power supplied to the model train through the tracks. For example, a positive DC signal can be used to actuate a train whistle, while a negative DC signal can actuate a train bell. Examples of such prior art control systems are described in U.S. Pat. No. 5,749,547 to Young et al.
It is also known in the prior art to provide a model railway train car with a searchlight controlled by the voltage from the transformer or with a searchlight that can be turned on and off. The searchlight comprises an incandescent light bulb that outputs uncollimated, broad-band white light and may be turned on and off as the model railway train car passes over a special track section with an electromagnet for actuating a switch in the searchlight car. Such a light is typically not controllable by the train operator beyond the ON and OFF states and then only by directing the model railway train over the special track section. The searchlight is not accompanied by a sound effect.
In a distinctly different art from model railway trains, laser light shows have become an increasingly prominent part of mass entertainment. Such laser light shows are produced by devices such as the Star Graphics Laser Sign.TM. sold by Holograms & Lasers International of Houston, Tex., U.S.A., and the Black Widow and Laser Graphics FX sold by American DJ Supply, Inc., of Los Angeles, Calif., U.S.A. Such devices use low-powered lasers, typically in the 5 mW to 300 mW range, with scanning mirror assemblies to project a pattern of light. The pattern can be anything from an abstract pattern, such as a lissajous curve, to a recognizable image or even text. However, the known laser light show devices are generally fixed in position, and the pattern is visible only on a projection screen area that must be in shadow. In particular, a laser beam passing through a medium such as the surrounding air is not visible from the side because of the coherence of the laser beam unless there is enough of a scattering medium, such as smoke, in the air to scatter the laser light and thus make the laser beam visible.